The present invention relates to plumbing apparatus, and pertains more particularly, to an improved fill valve assembly for flush systems used in gravity flush toilets.
Conventional toilets typically employ a generally rectangular porcelain tank mounted immediately above a porcelain bowl from which from a quantity of water is rapidly drained in order to flush waste from the bowl into the sewer system. One very common design uses a flapper valve made of an elastomeric material that normally covers the drain outlet of the tank. When the flush handle on the outside of the tank is manually depressed the flapper valve is lifted and the head of water in the tank drains through the drain outlet into the bowl, thereby flushing the contents of the bowl into the sewer system. The flapper valve is designed with an inverted air chamber so that it initially floats as it is lifted away from the drain outlet in the bottom of the tank. This allows sufficient flushing water to flow into the bowl even if the user immediately releases the flush halide. When the water level in the tank drops, it is automatically refilled through a fill valve connected to a high pressure water supply line.
The typical fill valve for the tank comprises a ballcock valve mounted in the tank on top of a riser which extends through an opening in the bottom of the tank and is connected to a pressurized water line in the house. When the tank drains, a float connected to the ballcock valve descends. This activates the ballcock valve and it begins to refill the tank with water at a rate much slower than the rate at which water flows through the drain outlet. When the tank is nearly empty, the flapper valve doses. The tank continues to refill as the float connected to the ballcock rises. At the same time water from the ballcock valve enters an overflow tube and refills the bowl to the normal standing water level to provide a trap seal. Once the float reaches a predetermined height indicating that the tank is full, the ballcock valve completely turns OFF.
The foregoing conventional arrangement is still widely used today and has been adapted to toilet designs of the lowboy design wherein the tank is shallow and is normally molded into the toilet bowl. The valve is mounted on the top of the riser in a number of ways, but must be permanent for the life of the product, once installed. Many of the installations do not provide a permanent seal. The tank is shallow and the plumbing code requires a sheath around the riser to prevent backflow in case of pressure loss in the water supply line. The sheath is a tube that extends from the bottom of the tank above the water level in the tank and is sealed at the tank inlet providing an air chamber around the riser that is vented around the inlet of the riser to below the tank.
One major problem with these type valve assemblies is that the valve is usually threadably mounted on top of the riser with all axially compressible seal and can become slightly unthreaded sufficiently to allow leakage. This can allow backflow of water from the tank into the supply line, and/or leakage of inlet water onto the floor of the bathroom and potentially causing severe damage.
Accordingly, it is desirable that some means be available to overcome the above problem of the prior art.